title: Reversible near-infrared pH probes based on benzo[a]phenoxazine.
abstract: Several benzo[a]phenoxazine derivatives containing substituted N-aromatic groups are evaluated for their pH-dependent absorption and emission properties. Among the compounds exhibiting optical responses under near-neutral and subacid pH conditions, benzo[a]phenoxazine derivatives with an electron-withdrawing aromatic group attached to nitrogen of the imino group show potential application as near-infrared pH sensors. Three water-soluble pH probes based on benzo[a]phenoxazine with different pyridinium structures are designed and synthesized. Their reversible pH-dependent emissions in buffer solution containing 0.1% dimethyl sulfoxide (DMSO) locate in 625-850 nm with the fluorescent enhancement of 8.2-40.1 times, and their calculated pKa values are 2.7, 5.8, and 7.1, respectively. A composite probe containing the three benzo[a]phenoxazines shows a linear pH-emission relationship in the range of pH 1.9-8.0. Real-time detection of intracellular pH using an in vitro assay with HeLa cells is also reported.
authors.affiliation: College of Chemistry, Chemical Engineering and Material Science, Soochow University, Suzhou 215123, People's Republic of China.
authors.forename: Wu
authors.initials: W
authors.lastname: Liu
authors.forename: Ru
authors.initials: R
authors.lastname: Sun
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Ge
authors.forename: Yu-Jie
authors.initials: YJ
authors.lastname: Xu
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.forename: Jian-Mei
authors.initials: JM
authors.lastname: Lu
authors.forename: Isaum
authors.initials: I
authors.lastname: Itoh
authors.forename: Masataka
authors.initials: M
authors.lastname: Ihara
mesh_terms: D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007259:Infrared Rays; D061848:Optical Imaging; D055620:Optical Phenomena; D010078:Oxazines / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D010078:Oxazines; C039203:phenoxazine